1. Field of the Invention
The present invention relates to the field of downhole tools and, more particularly, to tools such as anchors, packers, etc. which have radially extendable elements for engaging the casing, well bore, or other well conduit. A typical packer, for example, includes a resilient packer element, formed of a suitable elastomer, which may be radially expanded to seal against the surrounding well conduit. Many packers also include an anchor assembly having radially extendable slips or other anchor elements for gripping the well conduit to hold the tool in a desired position. However, such anchors may also be incorporated in other types of tools.
Tools of the type described above may be generally classified according to the manner in which they are set and/or released. One broad category consists of hydraulic set tools in which the radially extendable elements are extended by pumping a suitable fluid down through the drill string or operating string on which the tool is supported. Another broad category consists of mechanically set packers, and these may be sub-divided into those which are set by rotary movement of the operating string and those which are set by strictly linear movement of the operating string. Of the latter sub-division, those which are set by downward movement of the drill string are generally referred to as "weight set" since the downward movement is usually effected by partially releasing the means supporting the string and allowing its own weight to carry it downwardly.
Each of these general types of tools has its own advantages over the other types. One of the primary advantages of the tools which are set by linear movement, and particular "weight set" tools, is their simplicity of construction and operation.